(1) Field of the Invention
The present invention relates to a die for use in rethreading or chasing threads on a stud, bolt or rod with a damaged area, and in particular to a simple to manufacture, easily aligned, two-section die that can be clamped above the damaged area.
(2) Description of the Prior Art
Studs, bolts and other threaded rods, referred to collectively herein as rods, are commonly rethreaded with a hexagonal rethreading die to repair thread damage. A normal rethreading die has a central opening with cutting or threading teeth facing into the opening for thread forming or cutting. The opening also includes relief areas to permit cuttings or debris to fall away from the area of the rod being repaired and to lubricate the teeth and rod.
In those instances where there is a need to repair a rod having damage at or near its unattached end, threading of a normal die onto the rod to repair the threads can be difficult or impossible to properly alignment the die threads to the thread pitch of the rod. In order to rethread rods with thread damage at or near the rod end, split or multi-section dies have been developed.
A split die is comprised of two or more sections that are joinable together to form the hexagonal rethreading die. More particularly, a two-section rethreading die is comprised of a pair of opposed die members cooperatively defining an inner opening and thread forming surfaces facing into the opening. The die members further define external wrench surfaces which together have a hexagonal surface.
This construction permits separation of the die sections so that the die can be positioned around an undamaged inboard part of the rod above the damaged section. After positioning around the rod, the die sections are clamped together with a socket wrench or other suitable tool and the die is rotated outwardly toward the segment with the damaged threads. For example, if the rod has right-hand threads, the die is rotated counterclockwise. As the die is rotated over the damaged segment, the threads are reformed by the die threads.
Several prior art patents describe split rethreading dies. For example, U.S. Pat. No. 4,572,032 to Kinzler describes a hinged split die comprised of two die sections that are hinged together at one side to form a clam shell type die that opens for placement around the rod. An adjustable screw on the other side of the die controls the distance of separation between the die sections when the sections are closed. U.S. Pat. No. 6,206,620 also describes a hinged die comprised of two identical die segments that are hinged together.
U.S. Pat. No. 4,346,491 to Kraus et al. and U.S. Pat. No. 5,803,676 to Wienss describe rethreading dies comprised of two sections that are clamped together by special clamping tools. U.S. Pat. No. 1,416,059 to Piel describes a rethreading die, in which the die sections are held together by a circular spring. While not specifically described as a rethreading die, U.S. Pat. No. 1,366,884 describes a sectional nut comprised of two nut sections that are hinged together at one side. A register pin is used to align the sections on the opposite side and a flexible leaf spring is used to hold the nut sections together.
While the above dies are known in the prior art, there is still a need for a two-section replacement die that is economical to manufacture and which can be quickly and easily clamped around a rod having a damaged thread segment, particularly when the rod is in a confined location making opening of a hinged two-section die difficult or impossible.